Publications

Expertsâ€™ knowledge about optical technologies for spatial and spectral recording is logically structured and stored in an ontology-based knowledge representation with the aim to provide objective recommendations for recording strategies. Besides operational functionalities and technical parameters such as measurement principles, instruments, and setups further factors such as the targeted application, data, physical characteristics of the object, and external influences are considered creating a holistic view on spectral and spatial recording strategies. Through this approach impacting factors on the technologies and generated data are identified. Semantic technologies allow to flexibly store this knowledge in a hierarchical class structure with dependencies, interrelations and description logic statements. Through an inference system the knowledge can be retrieved adapted to individual needs.

Spatial and spectral recording of cultural heritage objects is a complex task including data acquisition, processing and analysis involving different technical disciplines. Additionally, the development of a suitable digitisation strategy satisfying the expectations of the humanities experts needs an interdisciplinary dialogue often suffering from misunderstanding and knowledge gaps on both the technical and humanities sides. Through a concerted discussion, experts from the cultural heritage and technical domains currently develop a so-called COSCH KR (Colour and Space in Cultural Heritage Knowledge Representation) platform that will give recommendations for spatial and spectral recording strategies adapted to the needs of the cultural heritage application. The platform will make use of an ontology through which the relevant parameters of the different domains involved in the recording, processing, analysis, and dissemination of cultural heritage objects are hierarchically structured and related through rule-based dependencies. Background and basis for this ontology is the fact that a deterministic relation exists between (1) the requirements of a cultural heritage application on spatial, spectral, as well as visual digital information of a cultural heritage object which itself has concrete physical characteristics and (2) the technical possibilities of the spectral and spatial recording devices. Through a case study which deals with the deformation analysis of wooden samples of cultural heritage artefacts, this deterministic relationship is illustrated explaining the overall structure and development of the ontology. The aim of the COSCH KR platform is to support cultural heritage experts finding the best suitable recording strategy for their often unique physical cultural heritage object and research question. The platform will support them and will make them aware of the relevant parameters and limitations of the recording strategy with respect to the characteristics of the cultural heritage object, external influences, application, recording devices, and data.

43rd Conference of Computer Applications and Quantitative Methods in Archaeology, CAA 2015, Siena, Book of Abstracts.

Constant technological progress results in new possibilities to produce reliable and rich spatial data of cultural heritage objects: for instance, museums have started to digitize their collections, more and more archaeological excavations or features and entire CH buildings have been documented in 3D. It is now necessary to establish connections among different CH disciplines and several technical disciplines, and to work on collaborative projects.

Technicians and CH experts together evaluate the best technique for specific CH object documentation, implementation and use. This discussion arises from the knowledge gaps of each counterpart in respect to the other discipline. Projects such as Agora 3D (see below) clearly demonstrate the need for an evaluation of the different available techniques.

In order to make optimal use of these technological capabilities, it is important to identify and name the information required to best serve the reasoning processes in these application fields. Correspondingly it is necessary to know about the characteristics of digitization techniques producing the content adapted to the needs of the applications. Due to the considerable complexity of instruments and processes producing the data, it is helpful to have a clear structure which relates the capabilities of the instruments to the requirements of the applications.

The COST Action TD1201 â€śColour and Space in Cultural Heritage (COSCH)â€ť takes this need into account, aiming to enhance the understanding among these disciplines. We will focus on the already listed, structured and evaluated available 3D technologies. At the same time, experts in spectral and CH research started to list, structure, and evaluate their knowledge. These evaluations yield a structure of technologies, and ultimately the techniques and instruments using their characteristics. The understanding of these characteristics provides insights for their potential applications. The ontology knowledge model accessible through so-called â€śCOSCHKR Appâ€ť provides a knowledge structure. It benefits from the development of semantic technologies from the Semantic Web framework. Semantics, which provide meanings, are captured through the conceptual structure and are defined through the ontology. The overall aim of this ontology is the development of a software tool to enable a better understanding of data acquisition techniques and their support to optimally realize cultural heritage applications.

43rd Conference of Computer Applications and Quantitative Methods in Archaeology, CAA 2015, Siena, Book of Abstracts.

Traditionally stone inscriptions or drawings are documented through pictures or rubbings. The latter ones represent an analogue copy of the stoneâ€™s surface and its features which are reproduced on paper. The disadvantage of this technique is the physical impact to the stone and the contained elements. Images reproduce the surface without contact. However, they might be affected by geometrical distortions and need appropriate lighting conditions to show the signs properly.

These problems will be avoided by means of non-contact 3D measuring techniques, like fringe projection. Such high resolution 3D techniques provide an exact geometrical copy of the original petroglyph, offering better results in legibility compared to traditional techniques. Moreover, it gives a more objective base for analysis and has less impact on the sometimes sensitive and eroded surfaces. Furthermore 3D data allows more extensive and further possibilities in processing and gives better preconditions for the interpretation.

However, depending on factors like resolution, scanned surface and degree of overlap between individual scans original 3D datasets may represent large up to really massive volumes of data. An effective use of such datasets can only be realised if they are condensed and prepared in a suitable way. This means reduction of the data volume, minimising any disturbing influence emerging from the spatial shape of the surface and emphasizing relevant information. The corresponding preparation of the data will then be a good base for a interpretation performed by the human science specialist through an adapted visualization. In addition the data should be prepared for high performance presentation to a wider community via the internet.

Processed digital copies of the Petroglyphs are visualised in order to enable the user to inspect the processed scans of the objects. By inspecting the scans the application provides a mass of functionality for achieving different views into the Petroglyphs and their appearance. This comprises on the one hand a simple 2D viewer for the processed data, and on the other hand a 3D viewer with interactive changeable light positions and water levels as well as a viewer for applying various lookup tables (colour), predefined image filters (convolution) and template matching (matching) regarding individual characters.

Provided functionality of the 3D viewer is based on features of 3D computer graphics. Surface normal vectors from the grey values of the processed scans and a light direction vector from an interactively changeable light source are computed. In addition shading is complemented by water filling, whereby the gray values are limited by the water level selected. Individual modifications are possible to improve the subjective impression by the user, trying to support him in his process of interpretation. Interactive changes of the light source directly affect the shading of the surface and provide a better idea of the 3D surface of the inscription board. Dynamic virtual water filling enables the user to obtain an even better impression of the depth of the individual characters and emphasise weathered characters.

The paper will explain the developed techniques and document its potential at selected data sets.

Abstract.Â Accurate recognition of airborne pollen taxa is crucial for understanding and treating allergic diseases which affect an important proportion of the world population. Modern computer vision techniques enable the detection of discriminant characteristics. Apertures are among the important characteristics which have not been adequately explored until now. A flexible method of detection, localization, and counting of apertures of different pollen taxa with varying appearances is proposed. Aperture description is based on primitive images following the bag-of-words strategy. A confidence map is estimated based on the classification of sampled regions. The method is designed to be extended modularly to new aperture types employing the same algorithm by building individual classifiers. The method was evaluated on the top five allergenic pollen taxa in Germany, and its robustness to unseen particles was verified.